A breast pump system is used for extracting milk from a breast of a user. A breast pump may be used if the baby or infant is not itself able to express milk from the breast, or if the mother is separated from the baby or infant, for example, if away from the baby at work. The use of a breast pump system to express milk may also be used to stimulate and increase milk production in women with a low milk supply.
Breast pump systems make use of a vacuum to induce milk expression from a nursing mother's breast. The pumping action of the device draws the milk from the nipple to a collection vessel, and the pressure and/or frequency may be adjustable to the preferences of the mother.
A breast pump system generally comprises a breast pump, acting as an expression unit, and an operating unit to operate the breast pump. The expression unit has a funnel in which a user's breast is receivable, and a receptacle in which the expressed milk is collected. The operating unit comprises a vacuum pump driven by a motor. The operating unit and the expression unit may be separated from each other and connected by a tube. Alternatively, the operating unit is mounted to the expression unit.
In use, the vacuum pump applies a vacuum to the breast received in the funnel. That is, when a user's breast is received in the funnel a sealed air system is created between the user's breast and the vacuum pump so that the vacuum pump is able to generate a vacuum which acts on the user's breast. In one arrangement, the vacuum in the funnel is created indirectly. The reduction in pressure generated by the vacuum pump acts on a membrane received in a chamber in the expression unit which deforms to cause a reduction in pressure in the funnel. Therefore, a vacuum is applied to the breast which induces milk to be expressed.
It is known to provide a breast pump system in which a cyclical pressure differential is applied to the breast. In such an arrangement, a pressure release valve is disposed in the operating unit. After a desired reduction in pressure has been established, the valve is opened to allow the vacuum acting on the membrane to be released. As the pressure from the vacuum is released, the membrane deforms back into its original position and the vacuum acting on the user's breast is reduced. By cyclically opening and closing the valve a cyclic pressure profile in order to express milk from the breast is achieved.
However, one problem with the above arrangement is that if the valve fails to open then the vacuum acting on the user's breast is maintained which may cause discomfort or injury to a user and/or may prevent the user from removing their breast from the vacuum pump.